# Author: Fred L. Drake, Jr. # fdrake@acm.org # # This is a simple little module I wrote to make life easier. I didn't # see anything quite like it in the library, though I may have overlooked # something. I wrote this when I was trying to read some heavily nested # tuples with fairly non-descriptive content. This is modeled very much # after Lisp/Scheme - style pretty-printing of lists. If you find it # useful, thank small children who sleep at night. """Support to pretty-print lists, tuples, & dictionaries recursively. Very simple, but useful, especially in debugging data structures. Classes ------- PrettyPrinter() Handle pretty-printing operations onto a stream using a configured set of formatting parameters. Functions --------- pformat() Format a Python object into a pretty-printed representation. pprint() Pretty-print a Python object to a stream [default is sys.sydout]. saferepr() Generate a 'standard' repr()-like value, but protect against recursive data structures. """ from types import DictType, ListType, TupleType, StringType import sys try: from cStringIO import StringIO except ImportError: from StringIO import StringIO __all__ = ["pprint","pformat","isreadable","isrecursive","saferepr", "PrettyPrinter"] # cache these for faster access: _commajoin = ", ".join _sys_modules = sys.modules _id = id _len = len _type = type def pprint(object, stream=None): """Pretty-print a Python object to a stream [default is sys.sydout].""" printer = PrettyPrinter(stream=stream) printer.pprint(object) def pformat(object): """Format a Python object into a pretty-printed representation.""" return PrettyPrinter().pformat(object) def saferepr(object): """Version of repr() which can handle recursive data structures.""" return _safe_repr(object, {}, None, 0)[0] def isreadable(object): """Determine if saferepr(object) is readable by eval().""" return _safe_repr(object, {}, None, 0)[1] def isrecursive(object): """Determine if object requires a recursive representation.""" return _safe_repr(object, {}, None, 0)[2] class PrettyPrinter: def __init__(self, indent=1, width=80, depth=None, stream=None): """Handle pretty printing operations onto a stream using a set of configured parameters. indent Number of spaces to indent for each level of nesting. width Attempted maximum number of columns in the output. depth The maximum depth to print out nested structures. stream The desired output stream. If omitted (or false), the standard output stream available at construction will be used. """ indent = int(indent) width = int(width) assert indent >= 0 assert depth is None or depth > 0, "depth must be > 0" assert width self.__depth = depth self.__indent_per_level = indent self.__width = width if stream: self.__stream = stream else: self.__stream = sys.stdout def pprint(self, object): self.__stream.write(self.pformat(object) + "\n") def pformat(self, object): sio = StringIO() self.__format(object, sio, 0, 0, {}, 0) return sio.getvalue() def isrecursive(self, object): self.__recursive = 0 self.__repr(object, {}, 0) return self.__recursive def isreadable(self, object): self.__recursive = 0 self.__readable = 1 self.__repr(object, {}, 0) return self.__readable and not self.__recursive def __format(self, object, stream, indent, allowance, context, level): level = level + 1 objid = _id(object) if objid in context: stream.write(_recursion(object)) self.__recursive = 1 self.__readable = 0 return rep = self.__repr(object, context, level - 1) typ = _type(object) sepLines = _len(rep) > (self.__width - 1 - indent - allowance) write = stream.write if sepLines: if typ is DictType: write('{') if self.__indent_per_level > 1: write((self.__indent_per_level - 1) * ' ') length = _len(object) if length: context[objid] = 1 indent = indent + self.__indent_per_level items = object.items() items.sort() key, ent = items[0] rep = self.__repr(key, context, level) write(rep) write(': ') self.__format(ent, stream, indent + _len(rep) + 2, allowance + 1, context, level) if length > 1: for key, ent in items[1:]: rep = self.__repr(key, context, level) write(',\n%s: %s' % (' '*indent, rep)) self.__format(ent, stream, indent + _len(rep) + 2, allowance + 1, context, level) indent = indent - self.__indent_per_level del context[objid] write('}') return if typ is ListType or typ is TupleType: if typ is ListType: write('[') endchar = ']' else: write('(') endchar = ')' if self.__indent_per_level > 1: write((self.__indent_per_level - 1) * ' ') length = _len(object) if length: context[objid] = 1 indent = indent + self.__indent_per_level self.__format(object[0], stream, indent, allowance + 1, context, level) if length > 1: for ent in object[1:]: write(',\n' + ' '*indent) self.__format(ent, stream, indent, allowance + 1, context, level) indent = indent - self.__indent_per_level del context[objid] if typ is TupleType and length == 1: write(',') write(endchar) return write(rep) def __repr(self, object, context, level): repr, readable, recursive = _safe_repr(object, context, self.__depth, level) if not readable: self.__readable = 0 if recursive: self.__recursive = 1 return repr # Return triple (repr_string, isreadable, isrecursive). def _safe_repr(object, context, maxlevels, level): typ = _type(object) if typ is StringType: if 'locale' not in _sys_modules: return `object`, 1, 0 if "'" in object and '"' not in object: closure = '"' quotes = {'"': '\\"'} else: closure = "'" quotes = {"'": "\\'"} qget = quotes.get sio = StringIO() write = sio.write for char in object: if char.isalpha(): write(char) else: write(qget(char, `char`[1:-1])) return ("%s%s%s" % (closure, sio.getvalue(), closure)), 1, 0 if typ is DictType: if not object: return "{}", 1, 0 objid = _id(object) if maxlevels and level > maxlevels: return "{...}", 0, objid in context if objid in context: return _recursion(object), 0, 1 context[objid] = 1 readable = 1 recursive = 0 components = [] append = components.append level += 1 saferepr = _safe_repr for k, v in object.iteritems(): krepr, kreadable, krecur = saferepr(k, context, maxlevels, level) vrepr, vreadable, vrecur = saferepr(v, context, maxlevels, level) append("%s: %s" % (krepr, vrepr)) readable = readable and kreadable and vreadable if krecur or vrecur: recursive = 1 del context[objid] return "{%s}" % _commajoin(components), readable, recursive if typ is ListType or typ is TupleType: if typ is ListType: if not object: return "[]", 1, 0 format = "[%s]" elif _len(object) == 1: format = "(%s,)" else: if not object: return "()", 1, 0 format = "(%s)" objid = _id(object) if maxlevels and level > maxlevels: return format % "...", 0, objid in context if objid in context: return _recursion(object), 0, 1 context[objid] = 1 readable = 1 recursive = 0 components = [] append = components.append level += 1 for o in object: orepr, oreadable, orecur = _safe_repr(o, context, maxlevels, level) append(orepr) if not oreadable: readable = 0 if orecur: recursive = 1 del context[objid] return format % _commajoin(components), readable, recursive rep = `object` return rep, (rep and not rep.startswith('<')), 0 def _recursion(object): return ("" % (_type(object).__name__, _id(object))) def _perfcheck(object=None): import time if object is None: object = [("string", (1, 2), [3, 4], {5: 6, 7: 8})] * 100000 p = PrettyPrinter() t1 = time.time() _safe_repr(object, {}, None, 0) t2 = time.time() p.pformat(object) t3 = time.time() print "_safe_repr:", t2 - t1 print "pformat:", t3 - t2 if __name__ == "__main__": _perfcheck()